Collected from old wood boards at an abandoned ranch house. Brown squamules up to about 1mm, several may be clumped together but each grouping is separate from the next, well developed squamules have a lobe like overhang on top of an attachment structure buried in disintegrating wood. Underside of thallus is without cortex [EDIT: Probably not true], white medulla visible. Cross-section of thallus shows thin medulla with thicker layer of green algal cells between it and the upper cortex. Perethecia Immersed apothecia showing as black dots on thallus surface (see squamule detail photo).

Catapyrenium, Placidium, Verrucaria, or something else entirely, without micro I can’t venture a good guess and didn’t find any photos that look right.

Occurs with Lecanora muralis, Caloplaca stipitata, Candelaria pacifica and others.


Squamule group showing perethecia as black immersed dots
Old abandoned ranch house
Substrate. Dark lichen strips in center of photo
Apothecia cross-section
Apothecia cross-section

Proposed Names

-46% (2)
Recognized by sight
14% (2)
Recognized by sight
46% (2)
Recognized by sight: Just a guess, known from the County, visually similar, but…
28% (1)
Recognized by sight: Subsquamulose areoles…

Please login to propose your own names and vote on existing names.

= Observer’s choice
= Current consensus


Add Comment
Difficult things aren’t they??
By: Jason Hollinger (jason)
2016-12-03 10:58:09 CST (-0500)
“Some day it will be nameable…”
By: J-Dar
2016-12-02 22:10:10 CST (-0500)

I finally pulled this specimen out a year later and put it under the compound scope. Armed with Knudsen’s 2011 discussion of Acarospora veronensis vs. Acarospora americana (Opuscula Philolichenum, 9: 45-75. 2011), I am inclined to go with _A. veronensis on the basis of hymenium height, which varied from 75-90µm (see last sentence in quotation below) and lack of perethecial crown. However, it is not bulletproof, so I left A. americana as “could be”, pending determination from Knudsen himself.

“On the macromorphological level, A. veronensis differs from A. americana in having areoles that are generally smaller (usually 0.3-0.5(-1.0) vs. usually 0.5-2.5 mm), lacking subsquamulose lobulation, parathecial crowns, and pruina. On the
micromorphological level, A. veronensis differs from A. americana in having a thin (to 15 μm) or indistinct parathecium (thus not forming an expanded parathecial crown), a generally lower hymenium ((65-80 vs. (90-)100-120(-150) μm)), and a shorter subhymenium (usually 15-20 vs. 30-40 μm). There are no substantial differences in ascus and ascospore size between the two species. Both species predominately have one apothecium per areole (fig. 1E). Reduced specimens of A. americana often are macroscopically indistinguishable from A. veronensis in America. The easiest way to separate A. veronensis from such reduced forms of A. americana is by its hymenium which is approximately 80 μm high.”

Jason means the fourth photo, by the way
By: Jason Hollinger (jason)
2015-07-03 23:58:14 CDT (-0400)

The extreme close-up with gray background.

Jason: no way for you to know this a priori, but by default we hide your file names from other users. Some people keep info in those names that they don’t want to share. Don’t ask me what! :) Just easiest to default to hiding that info except for personal use by the photographers themselves. You can change this behavior in your user preferences somewhere.

Colors off in some pics
By: J-Dar
2015-07-03 20:22:55 CDT (-0400)

The first several pics are with my cell phone and its flash, and they show the specimen much blacker than it is. The most accurate color is the single squamule clump under the microscope, DSC_0072. The thallus is brown, I could convince myself purplish-brown, but definitely not blackish or anywhere near that. It was 100F when collected, the lichen was very dry, and I have not done anything to it since then, so it is probably the same color now as then.

OK, thanks.
By: zaca
2015-07-03 20:11:44 CDT (-0400)

If the colours are accurate, it seems that the fresh material was more purple-brown than the dried specimen. Is that correct?

You are right
By: J-Dar
2015-07-03 20:03:03 CDT (-0400)

It was collected earlier in the week, and no, I don’t have any photos of it from the collection site other than the picture of the stairs at the bottom right, where you can only see brown specks.

I thought that
By: zaca
2015-07-03 19:49:54 CDT (-0400)

the photos were taken several hours (or days) after collected, but maybe I’m wrong.

You mean wet?
By: J-Dar
2015-07-03 19:43:59 CDT (-0400)

When you say “fresh” specimen? There was no color change to the thallus when wet. I think most of these pics are at least damp.

Good work J-Dar …
By: zaca
2015-07-03 19:04:45 CDT (-0400)

and nice comments by Jason.
I miss this discussion but this observation clearly show how one can see perithecia in apothecia (the reverse also applies). Sometimes is better to do not believe in what our eyes are seeing.
I would like to ask if there is any photo with the fresh specimen (I´m not yet trained to look at dried material).

Ha! I know what you mean!
By: Jason Hollinger (jason)
2015-07-03 17:56:55 CDT (-0400)

At least you’ve got a good specimen. Some day it will be nameable… but yes, maybe choose your battles more carefully at first. :)

I think I’ll wait…
By: J-Dar
2015-07-03 17:51:16 CDT (-0400)

I’m just getting through the common foliose species in my area, not sure why I bang my head over something like this! It’s just hard to look at a piece of wood with 6 or 8 species on it and be ok with naming just 1 or 2.

Worth a try
By: Jason Hollinger (jason)
2015-07-03 17:44:20 CDT (-0400)

Important character, at least. Some of the most important Acarospora characters are:

  • spot tests
  • how broadly attached or stipitate the areoles are
  • if (sub)squamulose, color of the underside
  • whether the algal layer is interrupted with bundles of cortical hyphae
  • how thick the paraphyses are near the base
  • does it have “large” spores (10µm or longer)

Obviously, some characters require microscopy. And even then, all of the above require a great deal of subtle interpretation. Even after years, I rarely feel confident.

Not to discourage, per se, just be prepared for hard work and a long haul! :)

Couldn’t get a color reaction
By: J-Dar
2015-07-03 17:28:54 CDT (-0400)

With C or KC. At 40x dissecting scope.

Yes, exactly
By: Jason Hollinger (jason)
2015-07-03 17:19:39 CDT (-0400)

This looks like Acarospora now. Still weird to see it on wood, but there it is. Very difficult genus.

…Unless you can get a C+ or KC+ reaction off of the cortex — it can be very difficult to see, usually best to apply it under a coverslip at 100x, but see what happens anyway. At least we have a good key to the North American C+ species (see appendix of Knudsen et al. 2011. Studies in lichens and lichenicolous fungi, no 15. Opuscula Philolichenum 9: 45-75).

Cross-section photos added
By: J-Dar
2015-07-03 17:04:54 CDT (-0400)

The cross-section view makes it look like an immersed apothecia, right? So if not a pyrenolichen, then maybe Acarospora as you suggested?

By: Jason Hollinger (jason)
2015-07-03 15:57:20 CDT (-0400)

If it’s a perithecium, you should see the hymenium completely enclosed in an exciple (even if it’s pale), with just a tiny opening at the top, often invisible at 40×.

If it’s an immersed apothecium that’s just masquerading as a perithecium, you should see the hymenium is exposed over a significant area clearly visible at 40×. The sides of the apothecium may curve inward a bit, but should never come close to touching like they do in a perithecium.

Verrucaria, in addition, usually has a black “involucrellum” covering at least the top of the perithecium, some times arching away from the sides. Apothecia never have any equivalent structure. But of course, there are a few species of Verrucaria that lack involucrellum. And Placidium sensu lato don’t have one, either.

What should be clear?
By: J-Dar
2015-07-03 15:38:03 CDT (-0400)
If no lower cortex Verrucaria would be the most likely
By: Jason Hollinger (jason)
2015-07-03 15:35:50 CDT (-0400)

Hopefully you aren’t making the same mistake I made recently on one of Andrew’s observations(!) — you’ve ruled out Acarospora for sure? Should be clear in section even under dissecting scope.